German Patent 2,751,753 discloses a corner joint and an angle piece. The corner joint disclosed in the German patent includes a first section having a C-shaped attaching portion and a second section arranged at an angle thereto and having a C-shaped attaching portion by means of a corner connector. The joint is used in particular for producing coach body shells of extruded sections. The sections to be joined have one or more C-shaped attaching portions having two parallel section legs and webs integrally formed on the free leg ends and directed towards one another. The corner connector has two legs which are at right angles to one another and bear against the outer surfaces of the section webs. The connector legs each have two through-holes through which screws are inserted. The screws are screwed into parallelogram nuts which grip with their short sides behind the section webs. This known corner connector permits rapid and precise assembly and has proved very successful. However, it has the disadvantage that it can transmit only slight bending forces in the direction perpendicular to the common plane of the two sections. Coach bodies which are produced with these known corner connectors are therefore less resistant to bending in the transverse direction of the coach body.